Probably Washington DC. I’ve been wanting to go there for a while, and this would save me the trouble of figuring out the best way to get there. I normally drive when I go on vacation, but that’s a bit too far, since I actually really hate the driving part, and it would take at least four solid days to drive all the way over there.
Somewhere in center-south Yellowstone would work, too, since a 50 mile radius would get you all of Yellowstone and a good portion of Grand Teton. Then again, I pretty much did stay there for a week straight a few years ago…